Texas Instruments MSP50C6xx - Manual (Page 323)

Implementation Details
5-27 Code Development Tools
declarations ( or function prototypes) are introduced by the mnemonic
cmm_func . We only allow the new style of function declarations /prototypes,
where the type of the arguments is declared within the function’s parentheses.
For example:
cmm_func bidon(int i1,char *i2) is valid, but:
cmm_func bidon(i1,i2) int i1,char *i2; is invalid.
Note: The exact implementation of the MSP50C6xx stack is as follows:
on CALL:
1) Increment R7
2) Transfer TOS (top of stack) register to *R7
3) Transfer return address to TOS register
on RET:
1) next PC = TOS
2) transfer *R7 to TOS
3) decrement R7
We can freely manipulate R7 before a CALL/Ccc and after a RET to load and
unload arguments to and from the stack. The TOS register should never be
altered in the body of a function.
5.6.4 Programming Example
The following example implements string multiplication (i.e., the multiplication
of 2 integer strings). The same source file (with the exception of the first line)
can be used for C– – or regular C. In the case of regular C, it has to be compiled
and linked with
cmm_func.c
#define _CMM /*must be present for C– –compiler ONLY*/
#ifdef _CMM
#else
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include “cmm_back.h”
#endif
#include “cmm_func.h”